This invention relates to a document handling system for copiers in which a set of individual documents may be maintained partially separated, but partially overlapping, during their recirculation to provide a compact system for the recirculative copying of individual documents.
For the faster xerographic and other document copiers now in commercial use, it is increasingly desirable to provide for automatic handling of the individual original documents being copied in order to utilize those higher speed copying capabilities. However, such documents can vary widely in sheet size, weight, thickness, material, condition, humidity, age, and value. The documents may have curls, wrinkles, tears, "dog-ears", cut-outs, overlays, paste-ups, tape, staples, adhesive areas, or other defects. Yet it is desirable to be able to automatically copy a set of documents with a mixture of sizes, types, and conditions. Further, it is desirable to automatically handle such documents with a relatively compact and inexpensive document handling system. Preferably the document handling system is one which may be placed over an existing or conventional external transparent copying platen (window) of a copier, and which can utilize the same existing or conventional optics system. That is, it is desirable that the automatic document handling system be readily removable from the platen area by the copier operator whenever desired to allow conventional manual copying of documents, such as books on the same copying platen.
An especially difficult document handling problem is the automatic separation of individual documents for copying from a stack or set of unseparated documents without damage to or wear of the documents. A desirable document separating system which lends itself to a compact and simple system is a retard type document separator as taught in U.S. Pat. No. 3,768,803, issued Oct. 30, 1973, to K. K. Stange. However, such retard type separators, if used to separate documents from the same document set a substantial number of times tend to cause wear to separation areas of the documents. Further, almost any type of document separator has an increased liklihood of document damage or document non-separation with an increase in the number of times separation is required, particularly for varied or defensive documents as described above.
Another highly desirable feature for an automatic document handling system for a copier is to provide document recirculation for pre-collation copying. As discussed, for example, in detail in U.S. Pat. No. 3,963,345 issued June 15, 1976, to D. J. Stemmle, et al., at Columns 1-4, such pre-collation copying systems provide a number of important advantages. The copies exit the copier in pre-collated sets, and do not require subsequent sorting in a sorter or collator. On-line finishing and/or removal of completed copy sets may be provided while additional copy sets are being made from the same document set. Any desired number of such copy sets may be made by making a corresponding number of recirculations of the document set in collated order past a copying station and copying each document once each time it recirculates.
However, a disadvantage of pre-collation copying systems is this fact that the documents must all be repeatedly recirculated and repeatedly individually copied the number of times equivalent to the desired number of copy sets. Thus, for example, to make 10 copy sets of a 5 (page) document set or book, one copy at a time would be made of each of the 5 document pages in this order: Pages 1, 2, 3, 4, 5; 1, 2, 3, 4, 5, etc.; repeated a total of 10 times to make the desired 10 copy sets. For bi-directional pre-collation copying this document copying sequence would, instead, be 1, 2, 3, 4, 5; 5, 4, 3, 2, 1; 1, 2, 3, 4, 5; etc. Thus, it may be seen that increased document handling is necessitated for a pre-collation copying system, as compared to a conventional post-collation copying system in which all the desired copies are made at one time from each document page and collated subsequently. In such a post-collation copying system the document set need only be circulated once to fill the bins of the copy sheet sorter or collator with the number of copy sets desired (limited in number, however, to the number of bins).
The increased document handling required for a pre-collation copying system increases the liklihood of document damage or wear, and particularly aggrevates the above-noted problems of document separation. A pre-collation copying system renders much more undesirable a document handling system in which the individual documents must be separated from the remainder of the documents in the document set for each recirculation thereof. Thus, it is highly desirable to have the documents pre-separated in some manner prior to their multiple recirculation for copying. One such system is disclosed in the above-cited U.S. Pat. No. 3,963,345 on pre-collation copying.
The present invention is intended to overcome or minimize the above-discussed problems and disadvantages. It provides a simple, compact, automatic pre-collation document handling system in which the individual documents are effectively maintained pre-separated for any desired number of recirculations, yet in which the document set may be maintained in a compact manner, and recirculated in a short and simple document handling path, to minimize document damage, and to maximize the ability to reliably recirculate different or defective documents, and to reliably copy each individual document sheet on each document recirculation. The system disclosed herein is particularly suitable for, and compatible with, conventional copier platens and optics systems. It is also suitable for use as a removable or auxilary document handling system, removably overlying an existing or conventional platen to selectively allow use of that same platen and its associated optics for manual or other non-pre-collation copying. However it is not limited thereto.